Compression riveter



H. R. FISCHER COMPRESSION RIVETER Original Filed Jan. 50, 1940 'April" 12, 1949;

INVENTOR flo/mw l1? Haws/2 ATTZZY Patented Apr. 12, 1949 COMPRESSION RIVETER Howard B. Fischer, Detroit, Mich., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Original application January 30, 1940, Serial No.

(1 this application Decemher 29, 1942, Serial No. 470,442

316,299. Divided an 3 Claims.

This invention relates to squeeze riveting and like machines and more particularly to means for applying the rivet setting pressure. This is a division of application Serial No. 316,299, filed January 30, 1940, now Patent No. 2,310,625, dated February 9, 1943.

One object of the invention is to transmit the motion of a reciprocable power piston to a parallel rivet setting plunger through a wedge movable with the piston and through a pivoted lever having arms engaged respectively with the wedge and with the plunger, the wedge being doubly inclined in order to move the plunger at diiierent speed and force ratios.

Another object of the invention is to caus the rivet set plunger to exert substantially the same ultimate pressure irrespective of the thickness of the work sheets.

The latter object is accomplished by making the second of the wedge inclines engaged by the pivoted lever of uniform slope so that the mechanical advantage varies but little during the rivet setting portion of the power stroke. In a comparable device of the prior art the mechanical advantage changes greatly during the power stroke, maximum pressure being not attained until near the end of the limit of movement of the wedge. As a result that device is suited for use only with sheets of uniform thickness. In riveting other, thicker, sheets the strokes of the rivet set plunger and of the wedge are shortened and the full rivet heading pressure cannot be applied.

Other objects and structural details of the invention will be apparent from the following description when read in conjunction with the accompanying drawings, wherein:

Fig. 1 is a view chiefly in longitudinal section, of a riveting unit embodying the mechanism of the invention, the parts being shown at the end of the return stroke which is their normal position; and

Fig. 2 is a view similar to Fig. 1 showing the parts at the end of a power stroke, and in full and dotted outline indicating respectively the positions assumed when the work sheets are thick and when they are, thin.

The machine disclosed herein as embodying the. mechanism of the present invention is a portable compression riveter which is light in weight and is adapted to be held or supported in the hands of the operator, when in use. Referring to the drawing, it will be seen that the principal supporting elements of the machine are a cylinder 5, an adapter 6, associated with the cylinder, and a U-shaped bracket 1 secured to the adapter.

A pair of guard plates I0 enclose the open sides of the bracket I. The adapter 6 fits into one end of the cylinder 5 and is held in place by screws (not shown) extending into the wall of the cylinder. The adapter extends a short distance beyond the end of the cylinder 5 and is secured to the side Walls (one shown) of the bracket l by a pair of tie rods 8 and a bolt 9. The lower or closed end of the bracket 1 is formed with a downwardly extending rib 20 to which is detachably secured a yoke H. A particular yoke H is shown here merely by way of illustration since any one of a plurality of difierently formed yokes may be attached to the rib 20; the selection of a particular yoke being determined by the requirements of the work to be done. Each yoke, however, is formed with an anvil head in which is positioned a die E2 in line with a rivet set plunger l3 movable within a projecting portion M of the bracket 1. The die l2 and plunger l3 cooperate as riveting members between which work sheets of varying thickness may be placed and joined by a rivet headed by the pressure of said plunger. The rivet set plunger I3 is urged upward, or away from the die I2 by a pair of springs l5 (one shown) tensioned between a pin it passed through the rivet set and a stud ll supported by one of the guide plates H0. The upper end of the rivet set plunger l3 contact-s an arm or shoulder formed on a lever 18 of the bell crank type which is pivotably mounted on a stub shaft l9 rigidly mounted between the side walls of the bracket 1. The outer end of the lever 18 is bifurcated to form a pair of arms Ilia which support a roller 2 I. The roller 2i is normally spaced slightly from the lower one of a pair of rollers 22 mounted on the tie rods 8, and a Wedge 23 is arranged to enter between the rollers 2| and 22 and thereby force the lever it in a counter-clockwise direction to press the rivet set plunger 13 toward the die l2. The wedge 23 is pivotally connected to the bifurcated lower end of a piston rod 24 which forms part of a piston assembly movable within the cylinder 5.

The piston assembly com-prises, in addition to the rod 24, a pair of pistons 25 and 26 secured to the rod 24 and movable through respective chambers 21 and 28 formed in the cylinder 5. The chamber 28 is of considerably less diameter than the chamber 21 and is formed in a reduced elongated portion of the cylinder, which portion may be used as a handle for the tool. The outer end of the chamber 28 is closed by a cap 29, and a piston rod bushing 3| positioned in the inner end of the chamber 28 acts as a seal between the chambers 21 and 28. To efiect reciprocation of the piston assembly through power and return strokes, pressure fluid is supplied to the tool from a remote source and may be admitted alternately to the chamber 2! in back of piston 25 and to the chamber- 28: in front of. piston"26,' the admission of fluid to one chamber being accompanied by a venting of the other chamber. In the former instance the assembly is driven downward (see Fig. 2) to force the wedge 23 between the rollers 2| and 22 and set the rivet, while in the latter instance the assembly is returned:to thestarting position of Fig. 1. Any suitable' means maybe provided for controlling the flow of pressurefluid, for example, a conventional dour-Way -va1ve. According to another and preferred method, valve means operating under the control of a hand lever 32 acts to admit pressure fluid selectively to the back of piston and constantly to the'front of piston 26. Immediately upon the release of the 'press'ure in chamber '2! "therefore the piston assembly' is retracted. In order that the continuou'sly applied return'pressure may be balanced duringthe: power stroke, pressure fluid is "directed to the-rear of piston "26 by means of a -passage 33 in themed 2d, this passage receiving fluid through a port" 34 communicating with the a'rea in back of piston 25.

-The wedge 23 projects through an opening 35 i-formediinlthe adapter 6 and the lowerendthereofmormally engages the roller 2!. The face of the 'we'dge adjacent the roller? is formed iiwlthi a'cam surface ma'de' up of two inclined surfaces 23aand '2'3b adapted to be placed successively in cooperativerelation with the roller 2|. -:During'the downward motion'ofthe wedge' 23 on-*the power stroke the roller 2| travels "first on inclined portion 23a; which, having a steep slope, *vir'i'llmove'rivet-set plunger l3fast'but without a high' workingpressure. As the wedge advances, 'the lever 'I8rocks counterclockwise about the pivot' ['9 away from the position shown in Fig.- 1, thereby increasing the effective length "of the mower arm of'the-lever which is represented by the-distance between the pivot l9 and the line of applied force which passes through the center ofrollerzl. The slope of the cam surface on the wedge becomes more gradual as theroller 2| enters uponportion 23band now theplunger' I3 is movedslower and with -greater pressure resulting from the'increasedmechanical advantage. With iahelements in the Fig/2 position,"the eifective length :of'thepower arm of the lever I8 is ap 'proachin'g its maximum amount and is changing only'in'arelatively slight degree in relation to the :1;

further rocking movement. As long as the-roller remains onportion 23b there is nosubstantial furtherchange-in the mechanical advantage be- "cause the surface 23b-is uniform in'slope and en- -l0 thereof, the slope, mechanical advantage and 'final rivet heading pressure will be substantially the same.

*What is claimed is:

1. Inapower operated machine, a mechanical 15 movement-comprising a, piston having a cam- -:ming-. surface'ithereon, a power plunger movable I iniaa-lineparallel to the line of movement of the piston, a housing for the piston and plunger, a stationary pivot in the housing, a bell crank lever 20 arranged between the foregoing lines and I mounted on the pivot to transmit movement-from the" piston cam to the plunger, and a roller carried 'bythe free end of the power arm'of the lever, said camming surface coactingfwlth sai'd roller 5 I to "move shed-everabout its pivot toward a, 'position of said lever relative to sa'i-d l-ines' wherein the-effective length or the power arm'of the lever acted upon by -the cam approximates its makilll'lllllbmld the rateof changeof eifectivlength 'of' the power arm is substantially at' its minimum, said lever having a shoulder integrally "formed thereon to actuate the plunger.

"2. A mechanical"movement, as in claim "1, in which the camming surface is uniformly inlined 35toward the 'line or movement --"of the plunger "thereby to rotate the" lever' to a'pproach a' position =of=parallelism with said line.

3. A mechanical movement, as in 'claim' lin 'whi'chthe shoulder is'formed on the side of the 40 lever away from the piston.

HOWARD R." FISCHER.

' REFERENCES CITED UNITED STATES PATENTS 5 Number "Name Date '-1';8l4',632 Rohr 'Ji1ly-l-4,I 1931 1,869,188 Eckman 'July *26, 1932 1,886,241 Chapman Nov. 1,"*1"932 1,905,047 'l'itorin Apr. 25,1933

'15 933,731 Hanna '-Nov." 7,- 1 933 2,040,663 Mallet et al May-12, 19.36

' 2,140,658 Van 'Sittert Dec. 20, 1 1 338 "2122417 08 Van 'Sittert Dec."10,-1940 233101525 Fischer -"Feb."'9,- 1-943 

